The present invention relates generally to IC (Integrated Circuit) wafer fabrication systems, and more particularly, to a mechanism for dispensing liquid onto the IC wafer with minimized back-splash to reduce bubble defects during fabrication of integrated circuits on the IC wafers.
Referring to FIG. 1, liquid such as solution used for fabrication of integrated circuits on an IC (Integrated Circuit) wafer 102 is dispensed from a nozzle 104 of the prior art onto a surface 103 of the IC wafer 102 as the IC wafer 102 spins. FIG. 1 shows a top view of the nozzle 104 placed across the diameter of the surface 103 of the IC wafer 102. FIG. 2 shows a side view of the nozzle 104 that is placed across the diameter of the surface 103 of the IC wafer 102 of FIG. 1. Elements having the same reference number in FIGS. 1 and 2 refer to elements having similar structure and function.
Referring to FIGS. 1 and 2, the nozzle 104 of the prior art includes a liquid chamber 106 that fills up with the liquid to be dispensed onto the surface 103 of the IC wafer 102. In addition, the nozzle 104 of the prior art includes a plurality of nozzle passages that carry and direct the liquid from the liquid chamber 106 onto the surface 103 of the IC wafer 102. The nozzle 104 includes a first nozzle passage 112, a second nozzle passage 114, a third nozzle passage 116, a fourth nozzle passage 118, a fifth nozzle passage 120, a sixth nozzle passage 122, and a seventh nozzle passage 124. (Note that the plurality of nozzle passages 112, 114, 116, 118, 120, 122, and 124 in FIGS. 1 and 2 are shown to be relatively large for clarity of illustration. However, a typical size of the each of the nozzle passages 112, 114, 116, 118, 120, 122, and 124 is approximately 0.5 millimeters).
These plurality of nozzle passages 112, 114, 116, 118, 120, 122, and 124 in the nozzle 104 of the prior art are directed vertically downward to be perpendicular to the surface 103 of the IC wafer 102. Each of these nozzle passages 112, 114, 116, 118, 120, 122, and 124 in the nozzle 104 of the prior art directs a respective liquid stream of the liquid from the liquid chamber 106 toward the surface 103 of the IC wafer 102 as the IC wafer 102 spins (for example in the clockwise direction as illustrated in FIGS. 1 and 2).
Thus, the first nozzle passage 112 carries and directs a first liquid stream 113 from the liquid chamber 106 toward the surface 103 of the IC wafer 102. Similarly, the second nozzle passage 114 carries and directs a second liquid stream 115 from the liquid chamber 106 toward the surface 103 of the IC wafer 102. The third nozzle passage 116 carries and directs a third liquid stream 117 from the liquid chamber 106 toward the surface 103 of the IC wafer 102. The fourth nozzle passage 118 carries and directs a fourth liquid stream 119 from the liquid chamber 106 toward the surface 103 of the IC wafer 102. The fifth nozzle passage 120 carries and directs a fifth liquid stream 121 from the liquid chamber 106 toward the surface 103 of the IC wafer 102. The sixth nozzle passage 122 carries and directs a sixth liquid stream 123 from the liquid chamber 106 toward the surface 103 of the IC wafer 102. The seventh nozzle passage 124 carries and directs a seventh liquid stream 125 from the liquid chamber 106 toward the surface 103 of the IC wafer 102.
In the prior art, each of these liquid streams 113, 115, 117, 119, 121, 123, and 125 is directed vertically downward to be perpendicular to the surface 103 of the IC wafer 102 as the IC wafer 102 spins. In addition, in the prior art, each of these liquid streams 113, 115, 117, 119, 121, 123, and 125 is typically dispensed aggressively onto the surface 103 of the IC wafer 102 with much pressure.
Unfortunately in the prior art, a relatively large amount of back-splash of liquid dispensed onto the surface 103 of the IC wafer 102 results. Referring to FIG. 2, a layer of liquid 130 is dispensed onto the surface 103 of the IC wafer 102 from the nozzle of the prior art 104. The surface 103 of the wafer 102 may have a layer of another material already deposited thereon. For example, the surface 103 of the wafer 102 may have a layer of photoresist 132 deposited thereon, and the layer of liquid 130 dispensed onto the IC wafer 102 may be developer solution for developing the layer of photoresist 132.
Referring to FIG. 2, as the liquid streams 113, 115, 117, 119, 121, 123, and 125 are aggressively directed vertically downward toward the IC wafer 102 to be perpendicular to the surface 103 of the IC wafer 102, back-splash of the liquid from the layer of liquid 130 on the IC wafer 102 results. With such back-splash, the liquid from the layer of liquid 130 bounce back up and away from the IC wafer 102, and bubbles form within the layer of liquid 130 on the IC wafer 102. Examples of such bubbles 140, 142, 144, and 146 are shown in FIG. 2 within the layer of liquid 130 on the IC wafer 102.
Such bubbles 140, 142, 144, and 146 are more prone to form with the nozzle 104 of the prior art because the liquid streams are directed toward the IC wafer 102 with relatively high pressure. In addition, such bubbles 140, 142, 144, and 146 are more prone to form with the nozzle 104 of the prior art because the liquid streams are directed vertically downward toward the IC wafer 102 to be perpendicular to the surface 103 of the IC wafer 102 as the IC wafer 102 is spinning. The velocity of the IC wafer 102 as the IC wafer 102 is spinning creates a force against a liquid stream when the liquid stream contacts the IC wafer 102, and such force contributes to the back-splash of the liquid when the liquid stream contacts the layer of liquid 130.
A bubble is located at a respective location within the layer of liquid 130 directly above the IC wafer 102, and such a bubble causes that respective location of the IC wafer 102 to be exposed to a low volume of liquid of the layer of liquid 130. However, proper exposure of the IC wafer 102 to a sufficient amount of liquid of the layer of liquid 130 dispensed onto the wafer 102 is desired for proper fabrication of integrated circuit structures on the IC wafer 102. With a bubble within the layer of liquid 130, the respective location of the IC wafer 102 having the bubble thereon may not be exposed to a sufficient volume of liquid of the layer of liquid 130. Such insufficient volume of liquid of the layer of liquid 130 at that location of the IC wafer 102 results in an integrated circuit defect at that location of the IC wafer 102, and such an integrated circuit defect may be referred to as a xe2x80x9cbubble defect.xe2x80x9d
Furthermore, a long-recognized important objective in the constant advancement of monolithic IC (Integrated Circuit) technology is the scaling-down of IC dimensions. Such scaling-down of IC dimensions reduces area capacitance and is critical to obtaining higher speed performance of integrated circuits. Moreover, reducing the area of an IC die leads to higher yield in IC fabrication. Such advantages are a driving force to constantly scale down IC dimensions. Referring to FIG. 2, as IC dimensions are further scaled down to submicron and nanometer dimensions, a bubble formed within the layer of liquid 130 is more likely to cause defects within integrated circuit structures with such scaled down dimensions on the IC wafer 102.
Thus, to generally minimize defects within integrated circuits on the IC wafer 102, and further in light of the importance of scaling down IC dimensions, a mechanism is desired for effectively dispensing liquid onto the IC wafer with minimized back-splash to reduce bubble defects during fabrication of integrated circuits on the IC wafers.
Accordingly, a general aspect of the present invention includes a nozzle apparatus and method for effectively dispensing liquid onto a surface of an IC (Integrated Circuit) wafer with minimized back-splash.
In one embodiment of the present invention, a nozzle includes a liquid chamber that fills up with the liquid to be dispensed onto the surface of the IC wafer, and the nozzle includes a plurality of nozzle passages. A nozzle passage carries and directs the liquid from the liquid chamber toward the surface of the IC wafer to provide a respective liquid stream from a respective location on the nozzle to a respective spot on the surface of the IC wafer as the IC wafer is spinning. In addition, according to a general aspect of the present invention, a nozzle passage is disposed within the nozzle at a respective angle with respect to the surface of the IC wafer such that the respective liquid stream from the nozzle passage is directed toward a velocity vector at the respective spot on the surface of the IC wafer where the respective liquid stream hits the surface of the IC wafer. For example, the respective angle of the nozzle passage with respect to the surface of the IC wafer may be 45xc2x0. In addition, the liquid stream is dispensed onto the surface of the IC wafer with relatively low pressure according to another aspect of the present invention.
The present invention may be used to particular advantage when the liquid is developer solution dispensed on the surface of the IC wafer for developing photoresist deposited on the surface of the IC wafer.
In this manner, the nozzle of the present invention dispenses liquid onto the surface of the IC wafer with minimized back-splash to reduce bubble defects within the integrated circuit fabricated on the surface of the IC wafer. The angling of the liquid stream toward the velocity vector on the IC wafer as the IC wafer spins reduces back-splash when the liquid stream hits the IC wafer. In addition, the liquid stream is applied onto the surface of the IC wafer with relatively low pressure.
These and other features and advantages of the present invention will be better understood by considering the following detailed description of the invention which is presented with the attached drawings.